Work continued, using the boric acid testicular lesion as a model. It was found that 10 daily intratesticular injections of insulin-like growth factor 1 could apparently stimulate recovery of spermatogenesis. This is absolutely unique; no growth factor has previouslt shown such activity. A repeat of the experiment is in process, testing not only a replicate of the previous design, but also adding the factor by pellet to the testis. In other parts of this study, it was found that large amounts of boron adversely affect bone strength, while lesser amounts increase bone breaking strength. This will be pursued to determine the lowest level at which such effects are discernable. Other aspects of this project include evaluating other rodent species for mechanisms of cell death. While rats show necrotic cell death after glycol ether exposure, guinea pigs show apoptotic cell death. Since the guinea pig is closer to the human in terms of its hematologic response to glycol ethers, this testicular difference (and relative insensitivity of the guinea pig) is interesting. Current studies are defining the degree of difference between the two species, and looking at hallmarks of the two processes. Learning more about this could help both identify the best models of human response, and understand the mechanisms, which would permit intelligent intervention.